I’m in a Logic class and this seems like a really simple concept but all the explanations given are so wordy that I can’t wrap my head around it.
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If you’re taking a logic class, then the meaning of words becomes very specific very fast, and don’t always match colloquial English – be aware.
In this case, an argument is valid if (and only if) it is impossible for the premises to be true and the conclusion to be false. For example:
Premises:
* A
* A and B -> C
* not C
Conclusion:
* not B
If the premises are true, the conclusion must be true, and you’ve got various things you can do to show this.
Note that like many mathy things, there are things that sound funny that nevertheless meet the definition:
Premise:
* All crocodiles are dead
Conclusion:
* All blue things are blue.
Premise:
* the empty set contains an element
Conclusion:
* the moon is made of green cheese
Both of these are valid, because it is not possible for the premises to be true and the conclusions to be false (in the first case because the conclusion is always true, and in the second because the premise is always false).
So be aware.
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